1. Field of the Invention
The invention relates generally to techniques of projecting patterned electromagnetic waves (e.g., patterned light) onto an object.
2. Description of the Related Art
There are already employed techniques of projecting patterned electromagnetic waves onto an object. See, for example, Japanese Patent Application Publication No. 2003-42736. The projecting techniques are utilized for projecting a precise pattern onto an object such as a semiconductor device board, for optically measuring the planar shape or solid shape of an object, and for other purposes.
A projecting device for projecting patterned electromagnetic waves onto an object is generally configured to include an electromagnetic wave source, a transformer for transforming an electromagnetic wave emitted from the electromagnetic wave source into a patterned electromagnetic wave, and an optical system for projecting the patterned electromagnetic wave emitted from the transformer, onto the object.
An exemplary version of such a projecting device is a projector for projecting patterned light as an example of patterned electromagnetic waves, onto an object. This projector is generally configured to include a light source, an optical transformer for transforming light emitted from the light source into patterned light, and an optical system for projecting the patterned light emitted from the optical transformer, onto an object.
The patterned light is generated to define, for example, a stripe configuration made up of alternating bright portions and dark portions. To this end, a conventional version of the optical transformer is made in the form of a photomask for spatially-periodically masking light emitted from the light source.
The photomask is fabricated to form an array in which light-transmissive portions corresponding to bright portions of the patterned light, and light-occluding portions corresponding to dark portions of the patterned light alternate. In general, the light-transmissive portions are in the form of air openings. Thus, a conventional photomask is provided for spatially-selectively transmitting or blocking light emitted from a light source, to thereby transform the light emitted from the light source into patterned light.
As a result, the above-described projecting technique can be employed for an exemplary purpose of projecting patterned light onto an object using the above-described photomask, to thereby optically measure the shape of the object. In this example, the shape of the object can be measured at an increasing level of resolution as the spatial interval of bright portions and dark portions arrayed in the patterned light, that is to say, the distance between adjacent ones of pattern lines forming the patterned light is shortened.
In addition, there is, in some cases, a need for improving the preciseness of the shape of patterned light to be used for projection, for satisfaction of an ultimate desire for improving the quality of projection by a projector for projecting precise patterned light, or an ultimate desire for improving the accuracy of measurement by a measuring device for optically measuring the planar shape or the solid shape of an object, by projecting patterned light onto the object. In these cases, there is a need for fabricating a photomask with increased precision.